Interphone master unit



FIG. 1 is front view of an interphone master unit illustrating my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a front perspective view thereof.

The broken lines shown in the drawings represent portions of the interphone master unit that form no part of the claimed design. 

CLAIM The ornamental design for an interphone master unit, as shown and described. 